Re: [PATCH] libata: rewrite SCSI host scheme to be one per ATA host

Daniela Engert
2009-04-22T15:10:55Z

Boaz Harrosh wrote:
> On 04/22/2009 12:23 PM, Jeff Garzik wrote:
>> Jeff Garzik wrote:
>>> Currently, libata creates a Scsi_Host per port. This was originally
>>> done to leverage SCSI's infrastructure to arbitrate among master/slave
>>> devices, but is not needed for most modern SATA controllers. And I
>>> _think_ it is not needed for master/slave if done properly, either.

>>> It may work with other controllers -- TRY AT YOUR OWN RISK. It will
>>> probably fail for master/slave configurations, and SAS & PMP also
>>> need looking at. It yielded this lsscsi output on my AHCI box:
>>>
>>> [0:0:0:0] disk ATA ST3500320AS SD15 /dev/sda
>>> [0:2:0:0] disk ATA G.SKILL 128GB SS 02.1 /dev/sdb
>>> [0:5:0:0] cd/dvd PIONEER BD-ROM BDC-202 1.04 /dev/sr0
>> For comparison, here is unmodified 2.6.30-rc3:
>>
>> [jgarzik@bd ~]$ lsscsi
>> [0:0:0:0] disk ATA ST3500320AS SD15 /dev/sda
>> [2:0:0:0] disk ATA G.SKILL 128GB SS 02.1 /dev/sdb
>> [5:0:0:0] cd/dvd PIONEER BD-ROM BDC-202 1.04 /dev/sr0
>>
>
> Could the master/slave be simply solved by emulating a SCSI LUN

Don't forget, there are ATAPI devices (some Sony CD burners and old
phase-changers come into mind) which *do* have multiple LUNs sitting
beyond the PATA port. I don't know if libata supports such setups (my
old OS/2 driver does) but one shouldn't hijack LUNs to emulate targets.

Ciao,
Dani